Heat transfer tube for heat exchanger, heat exchanger, refrigerating cycle apparatus, and air conditioner

ABSTRACT

To obtain a heat transfer tube for a heat exchanger or the like which can obtain predetermined heat transfer performance without increasing in-tube pressure loss. 
     High ridges  22 A having 10 to 20 rows with a predetermined height and low ridges  22 B with a height lower than the high ridges  22 A having 2 to 6 rows between the high ridges  22 A and the high ridges  22 A are provided on an inner face helically with respect to a tube axial direction.

TECHNICAL FIELD

The present invention relates to a heat transfer tube or the like for a heat exchanger in which a groove is provided in an inner face of the tube.

BACKGROUND ART

In a heat exchanger used for a refrigerating apparatus, an air conditioner, a heat pump and the like in general, a heat transfer tube in which a groove is formed in an inner face is arranged with respect to a plurality of fins aligned with a predetermined interval so as to penetrate a through hole provided in each fin. The heat transfer tube becomes a part of a refrigerant circuit in a refrigerating cycle apparatus, and a refrigerant (fluid) flows through inside the tube.

The groove in the inner face of the tube is processed so that a tube axial direction and a groove extending direction form a predetermined angle. Here, the tube inner face has recesses and ridges by forming the groove. A space in a recess portion is referred to as a groove portion, while a ridge portion formed by side walls of the adjacent grooves is referred to as a ridge portion.

The refrigerant flowing through the above heat transfer tube changes its phase (condensation or evaporation) through heat exchange with air outside the heat transfer tube or the like. In order to perform this phase change efficiently, heat transfer performance of the heat transfer tube has been improved by increase in a surface area inside the tube, fluid agitation effect by the groove portion, liquid film holding effect between the groove portions through a capillary action of the groove portion and the like (See Patent Document 1, for example).

PRIOR ART DOCUMENT Patent Document

[Patent Document 1] Japanese Unexamined Patent Application Publication No. 60-142195 (page 2, FIG. 1)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The above prior-art heat transfer tube uses a metal such as copper or copper alloy as a material in general. In the manufacture of a heat exchanger, a mechanical tube expanding method has been practiced in which a tube expanding ball is pushed into a tube so as to expand the heat transfer tube from the inside so as to bring the fin and the heat transfer tube into close contact and join them. However, at this time, the ridge portion is crushed by the tube expanding ball, pressure loss in the tube is increased, and heat transfer performance in the tube is lowered, which are problems.

The present invention was made in order to solve the above problems and has an object to provide a heat transfer tube which can obtain predetermined heat transfer performance without increasing an in-tube pressure loss, a heat exchanger using the heat transfer tube, a refrigerating cycle apparatus using the heat exchanger and the like.

Means for Solving the Problems

A heat transfer tube for a heat exchanger according to the present invention has high ridges formed with a predetermined height in ten to twenty rows and low ridges with a height lower than the high ridges in two to six rows between the high ridge and the high ridge, spirally with respect to a tube axial direction on an inner face of the tube.

ADVANTAGES

According to the heat transfer tube of the present invention, since the ridge portion in the groove in the tube inner face of the heat transfer tube is constituted by high ridges and low ridges, when the tube is expanded by a mechanical tube expanding method, the tube expanding ball is brought into contact with the high ridges, their top portions are crushed by about 0.04 mm and becomes flat and their ridge heights are lowered, but since the heights of the low ridges are lower than those of the high ridges by 0.04 mm or more, the low ridges are not deformed and the in-tube heat transfer performance can be improved without increasing the pressure loss as compared with a prior-art heat transfer tube. Also, if the heat transfer tube is expanded, an outer face of the heat transfer tube is processed into a polygonal shape, which can suppress spring back in the heat transfer tube to improve adhesion between the heat transfer tube and the fin, which is excellent in efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) and (b) are diagrams illustrating a heat exchanger 1 according to Embodiment 1 of the present invention.

FIGS. 2( a) and (b) are diagrams illustrating a shape of a tube inner face of a heat transfer tube 20 according to Embodiment 1.

FIG. 3 is a diagram illustrating a state of tube expansion by a mechanical tube expanding method.

FIG. 4 is a graph illustrating a relationship between the number of rows of a high ridge 22A and a heat exchange rate.

FIG. 5 is a diagram illustrating a shape of a tube inner face of a heat transfer tube 20 according to Embodiment 2.

FIG. 6 is a graph illustrating a relationship between a difference between a groove portion 21 and a ridge portion 22 and a heat exchange rate after tube expansion.

FIG. 7 is a diagram illustrating a shape of a tube inner face of the heat transfer tube 20 according to Embodiment 3.

FIG. 8 is a diagram illustrating a shape of a tube inner face of the heat transfer tube 20 according to Embodiment 4.

FIG. 9 is a graph illustrating a relationship between an apex angle α of the high ridge 22A and a heat exchange rate.

FIG. 10 is a configuration diagram of an air conditioner according to Embodiment 5 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a diagram illustrating a heat exchanger 1 according to Embodiment 1 of the present invention. In FIG. 1, the heat exchanger 1 is a fin tube heat exchanger widely used as an evaporator and a condenser of a refrigerating apparatus, an air conditioner and the like. FIG. 1( a) is a perspective view when the heat exchanger 1 is cut in a vertical direction, while FIG. 1( b) illustrates a part of a section.

The heat exchanger 1 is configured by a plurality of fins 10 for the heat exchanger and heat transfer tubes 20. The heat transfer tubes 20 are provided with respect to the fins 10 arranged in plural with a predetermined interval so as to penetrate through holes provided in each fin 10. The heat transfer tube 20 becomes a part of a refrigerant circuit in a refrigerating cycle apparatus, and a refrigerant flows through the inside of the tube. By transmitting heat of the refrigerant flowing through the inside of the heat transfer tube 20 and air flowing outside through the fins 10, a heat transfer area to become a contact face with air is expanded, and heat exchange between the refrigerant and the air can be performed efficiently.

FIG. 2 is a diagram illustrating a shape of a tube inner face of the heat transfer tube 20 according to Embodiment 1. FIG. 2 expands a portion of A in FIG. 1. FIG. 2( a) illustrates a state before tube expansion, while FIG. 2(b) illustrates a state after the tube expansion. The tube inner face of the heat transfer tube 20 of this embodiment has a groove portion 21 and a ridge portion 22 by forming grooves. The ridge portion 21 is constituted by two types of ridge portions: a high ridge 22A and a low ridge 22B. Here, a height of the low ridge 22B is lower than that of the high ridge 22A by 0.04 mm or more. However, if a difference between the high ridge 22A and the low ridge 22B is too large (if the low ridge 22B is too low), there is a possibility that the heat transfer performance is lowered such as a decrease in a surface area inside the tube or the like, and the difference is assumed to be close to 0.04 mm in this embodiment.

FIG. 3 is a diagram illustrating a state of tube expansion by a mechanical tube expanding method. In the heat exchanger 1 in this embodiment, first, a center part in the longitudinal direction is bent into a hair pin shape with a predetermined bending pitch to manufacture a plurality of hair pin tubes to become the heat transfer tubes 20. After the hair pin tube is passed through a through hole of the fin 10, the hair pin tube is expanded by the mechanical tube expanding method, and the heat transfer tube 20 is brought into close contact with the fin 10 and joined. The mechanical tube expanding method is a method in which a rod 31 having a tube expanding ball 30 with a diameter slightly larger than an inner diameter of the heat transfer tube 20 at a tip is passed through the inside of the heat transfer tube 20 to expand an outer diameter of the heat transfer tube 20 and bring it into close contact with the fin 10.

When the tube is expanded by the mechanical tube expanding method, through a contact with the tube expanding ball 30, a ridge top portion of the high ridge 22A is crushed to become flat, and the ridge height is lowered. On the other hand, since a ridge top portion of the low ridge 22B is lower than a height of the high ridge 22A to be crushed by 0.04 mm or more, no deformation occurs. Since a pressure is applied to the portion of the high ridge 22A in order to expand the tube instead of applied to all the ridge portions in the tube to insert the tube expanding ball 30 as before, the outer face of the heat transfer tube is processed into a polygonal shape. Therefore, spring back of the heat transfer tube can be suppressed. As a result, adhesion between the heat transfer tube and the fin is improved, and efficiency in heat exchange can be improved.

FIG. 4 is a graph illustrating a relationship between the number of rows of the high ridges 22A and a heat exchange rate. In FIG. 2, the high ridges 22A and the low ridges 22B are shown alternately for explanation in this embodiment, but in actuality, on the inner face of the heat transfer tube 20, ten to twenty rows of high ridges 22A are spirally formed in succession in the axial direction. Then, moreover, two to six rows of low ridges 22B are formed between the high ridge 22A and the high ridge 22A.

As described above, in the heat exchanger 1, ten to twenty rows of the high ridges 22A of the heat transfer tube 20 is set because when the tube is expanded, the tube expanding ball 30 is brought into contact with the high ridge 22A, its top portion is crushed by about 0.04 mm and becomes flat, and the height of the ridge is lowered, but if the number of rows of the high ridges 22A of the heat transfer tube 20 is smaller than 10, the ridge top portion of the low ridge 22B is also crushed to become flat, and the in-tube heat transfer performance is lowered. Also, if the number of rows of the high ridges is set at not less than 20, the number of rows of the low ridges 22B is decreased, and the in-tube heat transfer performance is lowered.

As described above, according to the heat exchanger 1 of Embodiment 1, the ridge portion 22 of the tube inner face of the heat transfer tube 20 is constituted by two types of ridge portions, that is, the high ridges 22A having a predetermined height and the low ridge ridges 22B lower than the high ridge 22A by 0.04 mm or more, the high ridges 22A are provided in ten to twenty rows on the tube inner face, and the low ridges 22B are provided in two to six rows between the adjacent high ridge 22A and the high ridge 22A, so that heat transfer performance in the heat transfer tube 20 can be improved. Also, since the tube expanding ball 30 expands the tube in contact only with the high ridges 22A, the outer face of the heat transfer tube 20 is processed into a polygonal shape, spring back of the heat transfer tube is suppressed, and close contact between the heat transfer tube and the fin can be achieved. Also, a heat exchange rate (ratio of heat quantities before and after passing through the heat transfer tube) can be increased, and energy saving can be promoted. Also, while decrease and high efficiency of the refrigerant in the refrigerant circuit are maintained, size reduction can be promoted.

Embodiment 2

FIG. 5 is a diagram illustrating a shape of a tube inner face of the heat transfer tube 20 according to Embodiment 2. A configuration of the heat exchanger 1 is the same as Embodiment 1. In FIG. 5, the same reference numerals are given to portions performing the same or corresponding roles as those of Embodiment 1 (the same applies to the embodiments below). In this embodiment, a difference H between the groove portion 21 and the ridge portion 22 after tube expansion will be described.

FIG. 6 is a graph illustrating a relationship between a difference between the groove portion 21 and the ridge portion 22 and the heat exchange rate after tube expansion. In the heat transfer tube 20, the larger the difference H between the groove portion 21 and the ridge portion 22 after the tube expansion is, the larger the heat transfer rate becomes such that a surface area in the tube is increased or the like. However, if the difference H between the groove portion 21 and the ridge portion 22 becomes 0.26 mm or more, an increase amount of pressure loss becomes larger than an increase amount of the heat transfer rate, so that the heat exchange rate is lowered. On the other hand, if the difference H between the groove portion 21 and the ridge portion 22 is less than 0.1 mm, the heat transfer rate is not improved. From the above, in the heat transfer tube 20, the high ridge 22A and the low ridge 22B are formed so that the difference H between the groove portion 21 and the ridge portion 22 after the tube expansion is 0.1 to 0.26 mm.

As described above, according to the heat exchanger 1 of Embodiment 2, since the high ridge 22A and the low ridge 22B are formed so that the difference H between the groove portion 21 and the ridge portion 22 after the tube expansion is 0.1 to 0.26 mm, the heat transfer performance in the heat transfer tube 20 can be improved.

Embodiment 3

FIG. 7 is a diagram illustrating a shape of a tube inner face of the heat transfer tube 20 according to Embodiment 3. In Embodiment 3, in the heat exchanger 1, a distal end width W1 of a ridge top portion of the high ridge 22A is set in a range of 0.035 to 0.05 mm and a distal end width W2 of the low ridge 22B is set in a range of 0.03 to 0.035 mm in the heat transfer tube 20 after the tube expansion.

Regarding the distal end width W1 of the high ridge 22A, if it is set so that the distal end width W1 after the tube expansion becomes 0.035 mm or less, when the tube is expanded using the tube expanding ball 30, an upper part of the ridge top is crushed, and pressure by insertion is weakened. Thus, the tube expansion of the heat transfer tube 20 is insufficient, adhesion between the heat transfer tube 20 and the fin 10 is deteriorated, and drop in the heat transfer rate becomes remarkable. Also, if the distal end width W1 is made to be 0.05 mm or more, a sectional area is decreased in the groove portion 21, and a liquid film of the refrigerant becomes thick and the heat transfer rate is greatly lowered.

On the other hand, by setting the distal end width W2 of the low ridge 22B at 0.03 to 0.035 mm, a skirt width of the ridge is also narrowly formed, and by thinly forming as a whole, a heat transfer area is increased, and an in-tube heat transfer rate is increased.

As described above, according to the heat exchanger 1 of Embodiment 3, since the high ridges 22A and the low ridges 22B are formed so that the distal end width W1 of the ridge top portion of the high ridge 22A is in a range of 0.035 to 0.05 mm and the distal end width W2 of the low ridge 22B in a range of 0.03 to 0.035 mm, the heat transfer performance in the heat transfer tube 20 can be improved.

Embodiment 4

FIG. 8 is a diagram illustrating a shape of a tube inner face of the heat transfer tube 20 according to Embodiment 4 of the present invention. In Embodiment 4, in the heat exchanger 1, an apex angle α of the high ridge 22A is set at 15 to 30 degrees and the apex angle β of the low ridge 22B is set at 5 to 15 degrees in the heat transfer tube 20.

FIG. 9 is a graph illustrating a relationship between the apex angle α of the high ridge 22A and a heat exchange rate. Basically, the smaller the apex angle in the ridge portion 22 is, the larger the heat transfer area is increased in the heat transfer tube 20 as a whole, and the heat transfer rate is increased. However, if the apex angle α of the high ridge 22A is smaller than 15 degrees, workability at manufacture of the heat exchanger 1 is greatly lowered, and the heat exchange rate is lowered in the end. On the other hand, if the apex angle α is larger than 30 degrees, a sectional area at the groove portion 21 is decreased, the liquid film of the refrigerant overflows the groove portion 21, and even the ridge top portion is covered by the liquid film. Thus, the heat transfer rate is lowered.

On the other hand, by setting the apex angle β of the low ridge 22B at 5 to 15 degrees, the skirt width of the ridge is narrowly formed, and by thinly forming as a whole, the heat transfer area is increased, and the in-tube heat transfer rate is increased.

As described above, according to the heat exchanger 1 of Embodiment 4, since the high ridges 22A and the low ridges 22B are formed so that the apex angle α of the high ridge 22A is set at 15 to 30 degrees and the apex angle β of the low ridge 22B is set at 5 to 15 degrees, heat transfer performance in the heat transfer tube 20 can be improved.

Embodiment 5

FIG. 10 is a configuration diagram of an air conditioner according to Embodiment 5 of the present invention. In this embodiment, an air conditioner will be described as an example of a refrigerating cycle apparatus. The air conditioner in FIG. 10 is provided with a heat-source side unit (outdoor unit) 100 and a load-side unit (indoor unit) 200, and they are connected by a refrigerant piping so as to constitute a refrigerant circuit and circulate a refrigerant. In the refrigerant piping, piping through which a gas-phase refrigerant (gas refrigerant) flows is gas piping 300, and piping through which a liquid refrigerant (liquid refrigerant. It might be a gas-liquid two-phase refrigerant) flows is liquid piping 400. Here, as the refrigerant, an HC single refrigerant or a mixed refrigerant containing the HC refrigerant, R32, R410A, R407C, tetrafluoropropene (2,3,3,3-tetrafluoropropene, for example), carbon dioxide and the like are supposed to be used.

The heat-source side unit 100 in this embodiment is constituted by each device (means) of a compressor 101, an oil separator 102, a four-way valve 103, a heat-source side heat exchanger 104, a heat-source side fan 105, an accumulator 106, a heat-source side throttle device (expansion valve) 107, an inter-refrigerant heat exchanger 108, a bypass throttle device 109, and a heat-source side controller 111.

The compressor 101 has an electric motor 6 described in the above embodiment and intakes the refrigerant and compresses the refrigerant to turn it into a high-temperature and high-pressure gas state and flow it to the refrigerant piping. Regarding operation control of the compressor 101, by providing a master-side inverter circuit 2, a slave-side inverter circuit 3 and the like described in the above-mentioned embodiment in the compressor 101 and by changing an operation frequency arbitrarily, for example, a capacity (amount of the refrigerant to be fed out per unit time) of the compressor 101 can be finely changed.

Also, the oil separator 102 separates a lubricant discharged from the compressor 101 while being mixed in the refrigerant. The separated lubricant is returned to the compressor 101. The four-way valve 103 switches a flow of the refrigerant depending on a cooling operation and a heating operation on the basis of an instruction from the heat-source side controller 111. Also, the heat-source side heat exchanger 104 is constituted using the heat exchanger 1 described in the embodiments 1 to 4 to perform heat exchange between the refrigerant and air (outside air). For example, the heat exchanger functions as an evaporator in a heating operation and performs heat exchange between a low-pressure refrigerant flowing in through the heat-source side throttle device 107 and the air to evaporate and gasify the refrigerant. Also, it functions as a condenser in a cooling operation and performs heat exchange between a refrigerant flowing in from the four-way valve 103 side and compressed in the compressor 101 and the air to condense and liquefy the refrigerant. In the heat-source side heat exchanger 104, a heat-source side fan 105 is provided in order to perform heat exchange between the refrigerant and the air efficiently. The heat-source side fan 105 may also have an inverter circuit (not shown) to arbitrarily change the operation frequency of a fan motor and to finely change a rotation speed of the fan.

The inter-refrigerant heat exchanger 108 performs heat exchange between the refrigerant flowing through a major flow passage in the refrigerant circuit and the refrigerant branched from the flow passage and whose flow rate is adjusted by the bypass throttle device 109 (expansion valve). Particularly when there is a need to overcool the refrigerant in the cooling operation, the heat exchanger overcools the refrigerant and supplies it to the load-side unit 200. The inter-refrigerant heat exchanger 108 is also constituted using the heat exchanger 1 described in the embodiments 1 to 4.

A liquid flowing through the bypass throttle device 109 is returned to the accumulator 106 through the bypass piping 107. The accumulator 106 is means for accumulating an excessive liquid refrigerant, for example. The heat-source side controller 111 is constituted by a microcomputer or the like. The controller can perform a wired or wireless communication with a load-side controller 204 and controls operations of the entire air conditioner by controlling each means relating to the air conditioner such as operation frequency control or the like of the compressor 101 by inverter circuit control on the basis of data relating to detection of various detecting means (sensors) in the air conditioner, for example.

On the other hand, the load-side unit 200 is constituted by a load-side heat exchanger 201, a load-side throttle device (expansion valve) 202, a load-side fan 203, and a load-side controller 204. The load-side heat exchanger 201 is also constituted using the heat exchanger 1 described in the embodiments 1 to 4 to perform heat exchange between the refrigerant and air in a space to be air-conditioned. For example, the heat exchanger functions as a condenser in the heating operation, performs heat exchange between the refrigerant flowing in from the gas piping 300 and the air, condenses and liquefies the refrigerant (or turns it into gas-liquid two-phase), and flows it out to the liquid piping 400 side. On the other hand, in the cooling operation, the heat exchanger functions as an evaporator, performs heat exchange between the refrigerant brought into a low-pressure state by the load-side throttle device 202 and the air, makes the refrigerant get rid of heat in the air to evaporate and gasify, and flows it out to the gas piping 300 side. Also, in the load-side unit 200, the load-side fan 203 for adjusting flow of air for heat exchange is provided. An operation speed of the load-side fan 203 is determined by a user setting, for example. The load-side throttle device 202 is provided in order to adjust a pressure of the refrigerant in the load-side heat exchanger 201 by changing an opening degree.

Also, the load-side controller 204 is constituted by a microcomputer or the like and is capable of performing a wired or wireless communication with the heat-source side controller 111, for example. On the basis of an instruction from the heat-source side controller 111 and an instruction from a resident or the like, the controller controls each device (means) of the load-side unit 200 so that the inside of a room becomes a predetermined temperature, for example. Also, the controller transmits a signal including data relating to detection by detecting means provided in the load-side unit 200.

Next, an operation of the air conditioner will be described. At first, a basic refrigerant circulation in the refrigerant circuit during the cooling operation will be described. A high-temperature and high-pressure gas refrigerant discharged from the compressor 101 by a driving operation of the compressor 101 is condensed while passing through the heat-source side heat exchanger 104 from the four-way valve 103 and flows out of the heat-source side unit 100 as a liquid refrigerant. The refrigerant flowing into the load-side unit 200 through the liquid piping 400 is pressure-adjusted by the opening-degree adjustment of the load-side throttle device 202, and a low-temperature and low-pressure liquid refrigerant passes through the load-side heat exchanger 201, evaporates and flows out. Then, the refrigerant passes through the gas piping 300 and flows into the heat-source side unit 100 and is sucked into the compressor 101 through the four-way valve 103 and the accumulator 106, pressurized again and discharged, which makes circulation.

Also, a basic refrigerant circulation in the refrigerant circuit in the heating operation will be described. The high-temperature and high-pressure refrigerant discharged from the compressor 101 by the driving operation of the compressor 101 flows from the four-way valve 103 into the load-side unit 200 through the gas piping 300. In the load-side unit 200, the refrigerant is pressure-adjusted by the opening-degree of the load-side throttle device 202, being condensed while passing through the load-side heat exchanger 201, and becomes an intermediate-pressure liquid or a gas-liquid two-phase refrigerant to flow out of the load-side unit 200. The refrigerant flowing into the heat-source side unit 100 through the liquid piping 400 is pressure-adjusted by the opening-degree of the heat-source side throttle device 107, being evaporated while passing through the heat-source side heat exchanger 104, becomes a gas refrigerant and sucked into the compressor 101 through the four-way valve 103 and the accumulator 106 to be circulated by being pressurized and discharged as described above.

As described above, according to the air conditioner of Embodiment 5, since the heat exchanger 1 of Embodiments 1 to 4 having a high heat exchange rate is used as an evaporator and a condenser for the heat-source side heat exchanger 104 and the inter-refrigerant heat exchanger 108 of the heat-source side unit 100 and the load-side heat exchanger 201 of the load-side unit 200, a COP (Coefficient of Performance: energy consumption efficiency) or the like can be improved, and energy saving or the like can be promoted.

Example

An example will be described below in comparison with a comparative example that departs from the scope of the present invention. As shown in Table 1, heat exchangers 20 with an outer diameter of 7 mm, a bottom thickness of the groove 21 of 0.25 mm, a lead angle of 30 degrees, and the number of high ridge rows of 10 and 20 (Example 1 and Example 2) are produced. Also, as comparative examples, heat exchangers with the outer diameter of 7 mm, the bottom thickness of the grove 21 of 0.25 mm, and the number of high ridge rows of 5 and 30 are produced (Comparative Example 1 and Comparative Example 2).

TABLE 1 Row number Outer Bottom (high Heat diameter thickness Lead ridges) exchange (mm) (mm) angle (—) rate Comparative 7 0.25 30 degrees 5 99 Example 1 Example 1 7 0.25 30 degrees 10 101.3 Example 2 7 0.25 30 degrees 20 101 Comparative 7 0.25 30 degrees 30 99.5 Example 2

As obvious from Table 1, the heat exchangers 1 in Example 1 and Example 2 both have a higher heat exchange rate than the heat exchangers in Comparative Example 1 and Comparative Example 2, and the in-tube heat transfer performance is improved.

Next, as shown in Table 2, the heat exchangers 1 with an outer diameter of 7 mm, a bottom thickness of the groove 21 of 0.25 mm, a lead angle of 30 degrees, and groove depths after tube expansion of 0.10 mm and 0.26 mm (Example 3 and Example 4) are produced. Also, as comparative examples, heat exchangers with the outer diameter of 7 mm, the bottom thickness of the groove 21 of 0.25 mm, the lead angle of 30 degrees, and groove depths after tube expansion of 0.05 mm and 0.3 mm, respectively, are produced (Comparative Example 3 and Comparative Example 4).

TABLE 2 Groove depth after Outer Bottom tube Heat diameter thickness Lead expansion exchange (mm) (mm) angle (mm) rate Comparative 7 0.25 30 degrees 0.05 99 Example 3 Example 3 7 0.25 30 degrees 0.1 101.5 Example 4 7 0.25 30 degrees 0.26 101.2 Comparative 7 0.25 30 degrees 0.3 99.4 Example 4

As obvious from Table 2, the heat exchangers 1 of Example 3 and Example 4 both have a higher heat exchange rate than the heat exchangers of Comparative Example 3 and Comparative Example 4, and the in-tube heat transfer performance is improved.

Next, as shown in Table 3, the heat exchangers with an outer diameter of 7 mm, a bottom thickness of the groove 21 of 0.25 mm, a lead angle of 30 degrees, and ridge-portion distal end widths of high ridges of 0.035 mm, 0.4 mm and 0.5 mm (Example 5, Example 6, and Example 7) are produced. Also, as comparative examples, heat exchangers with the outer diameter of 7 mm, the bottom thickness of the groove 21 of 0.25 mm, the lead angle of 30 degrees, and ridge-portion distal end widths of the high ridges of 0.025 mm and 0.6 mm, are produced (Comparative Example 5 and Comparative Example 6).

TABLE 3 Ridge- portion Outer Bottom distal end Heat diameter thickness Lead width exchange (mm) (mm) angle (mm) rate Comparative 7 0.25 30 degrees 0.025 99.2 Example 5 Example 5 7 0.25 30 degrees 0.035 101.2 Example 6 7 0.25 30 degrees 0.04 101.8 Example 7 7 0.25 30 degrees 0.05 101 Comparative 7 0.25 30 degrees 0.06 98 Example 6

As obvious from Table 3, all the heat exchangers 1 in Example 5, Example 6, and Example 7 have a higher heat exchange rate than the heat exchangers in Comparative Example 5 and Comparative Example 6, and the in-tube heat transfer performance is improved.

Next, as shown in Table 4, the heat exchangers 1 with an outer diameter of 7 mm, a bottom thickness of the groove 21 of 0.25 mm, a lead angle of 30 degrees, and apex angles of 15 degrees and 30 degrees (Example 8 and Example 9) are produced from aluminum. Also, as comparative examples, heat exchangers with the outer diameter of 7 mm, the bottom thickness of 0.25 mm, the lead angle of 30 degrees, and apex angles of 10 degrees and 40 degrees are produced (Comparative Example 7 and Comparative Example 8).

TABLE 4 Outer Bottom Apex Heat diameter thickness Lead angle exchange (mm) (mm) angle (degrees) rate Comparative 7 0.25 30 degrees 10 99 Example 7 Example 8 7 0.25 30 degrees 15 101 Example 9 7 0.25 30 degrees 30 101.3 Comparative 7 0.25 30 degrees 40 99.3 Example 8

As obvious from Table 4, the heat exchangers 1 of Example 8 and Example 9 both have a higher heat exchange rate than the heat exchangers in Comparative Example 7 and Comparative Example 8, and the in-tube heat transfer performance is improved.

INDUSTRIAL APPLICABILITY

In the above-described embodiment 5, regarding the heat exchanger according to the present invention, an application to an air conditioner is described. The present invention is not limited to these apparatuses but can be applied to other refrigerating cycle apparatus such as a refrigerating apparatus and a heat pump having a heat exchanger constituting a refrigerant circuit and to become an evaporator and a condenser.

REFERENCE NUMERALS

-   -   1: heat exchanger     -   10: fin     -   20: heat transfer tube     -   21: groove portion     -   22: ridge portion     -   22A: high ridge     -   22B: low ridge     -   30: tube expansion ball     -   31: rod     -   100: heat-source side unit     -   101: compressor     -   102: oil separator     -   103: four-way valve     -   104: heat-source side heat exchanger     -   105: heat-source side fan     -   106: accumulator     -   107: heat-source side throttle device     -   108: inter-refrigerant heat exchanger     -   109: bypass throttle device     -   110: heat-source side controller     -   200: load-side unit     -   201: load-side heat exchanger     -   202: load-side throttle device     -   203: load-side fan     -   204: load-side controller     -   300: gas piping     -   400: liquid piping     -   α: apex angle     -   H: difference between groove portion 21 and ridge portion 22         after tube expansion     -   W1: distal end width of ridge top portion of high ridge 22A     -   W2: distal end width of ridge top portion of low ridge 22B 

1. A heat transfer tube for a heat exchanger, wherein high ridges formed with a predetermined height in ten to twenty rows and low ridges formed with a height lower than said high ridges in two to six rows between said high ridge and said high ridge are provided on an inner face of the tube, spirally with respect to a tube axial direction.
 2. The heat transfer tube for the heat exchanger of claim 1, wherein a difference in height between said high ridges and said low ridges is 0.04 mm or more.
 3. A heat exchanger, wherein a plurality of fins for expanding an area for heat exchange and the heat transfer tube of claim 1 are joined by pressurizing and performing tube expansion from an inner face side of said heat transfer tube.
 4. The heat exchanger of claim 3, wherein heights in said high ridges after tube expansion of said heat transfer tube are 0.10 to 0.26 mm.
 5. The heat exchanger of claim 3, wherein a width of a distal end portion of said high ridge after tube expansion of said heat transfer tube is 0.035 to 0.05 mm and a width of a distal end portion of said low ridge is 0.03 to 0.035 mm.
 6. The heat exchanger of claim 3, wherein an apex angle of said high ridge is formed to be 15 to 30 degrees and an apex angle of said low ridge to be 5 to 15 degrees.
 7. A refrigerating cycle apparatus constituting a refrigerant circuit in which a compressor for compressing a refrigerant, a condenser for condensing said refrigerant by heat exchange, expanding means for decompressing the condensed refrigerant, and an evaporator for evaporating said decompressed refrigerant by heat exchange are connected by piping for circulating said refrigerant, wherein the heat exchanger of claim 3 is said condenser and/or evaporator.
 8. The refrigerating cycle apparatus of claim 7, wherein as said refrigerant, any of an HC single refrigerant, a mixed refrigerant containing the HC, R32, R410A, R407C, tetrafluoropropene, or carbon dioxide is used.
 9. An air conditioner, wherein cooling/heating of a target space is performed by the refrigerating cycle apparatus of claim
 7. 10. A heat exchanger, wherein a plurality of fins for expanding an area for heat exchange and the heat transfer tube of claim 2 are joined by pressurizing and performing tube expansion from an inner face side of said heat transfer tube.
 11. The heat exchanger of claim 4, wherein a width of a distal end portion of said high ridge after tube expansion of said heat transfer tube is 0.035 to 0.05 mm and a width of a distal end portion of said low ridge is 0.03 to 0.035 mm.
 12. The heat exchanger of claim 4, wherein an apex angle of said high ridge is formed to be 15 to 30 degrees and an apex angle of said low ridge to be 5 to 15 degrees.
 13. The heat exchanger of claim 5, wherein an apex angle of said high ridge is formed to be 15 to 30 degrees and an apex angle of said low ridge to be 5 to 15 degrees.
 14. A refrigerating cycle apparatus constituting a refrigerant circuit in which a compressor for compressing a refrigerant, a condenser for condensing said refrigerant by heat exchange, expanding means for decompressing the condensed refrigerant, and an evaporator for evaporating said decompressed refrigerant by heat exchange are connected by piping for circulating said refrigerant, wherein the heat exchanger of claim 4 is said condenser and/or evaporator.
 15. A refrigerating cycle apparatus constituting a refrigerant circuit in which a compressor for compressing a refrigerant, a condenser for condensing said refrigerant by heat exchange, expanding means for decompressing the condensed refrigerant, and an evaporator for evaporating said decompressed refrigerant by heat exchange are connected by piping for circulating said refrigerant, wherein the heat exchanger of claim 5 is said condenser and/or evaporator.
 16. A refrigerating cycle apparatus constituting a refrigerant circuit in which a compressor for compressing a refrigerant, a condenser for condensing said refrigerant by heat exchange, expanding means for decompressing the condensed refrigerant, and an evaporator for evaporating said decompressed refrigerant by heat exchange are connected by piping for circulating said refrigerant, wherein the heat exchanger of claim 6 is said condenser and/or evaporator.
 17. An air conditioner, wherein cooling/heating of a target space is performed by the refrigerating cycle apparatus of claim
 8. 